The present invention relates to a cassette type sheet feed appparatus for a copy machine or the like.
Cassette type sheet feed systems are especially advantageous for use in office copying machines, printing machines and the like since they offer convenience and facilitate automated sheet feed. In such a system, sheets of various standard sizes are provided in respectively sized cassettes, which are inserted into a frame. The system is found in two basic types; a first type in which only one cassette is insertable into the frame at once and a second type in which several cassettes are inserted into the frame at once in a vertically stacked arrangement and a selective feed means feeds sheets from only the selected cassette.
From the point of view of economy of manufacture, it is desirable to design the spaces in the frame which receive the cassettes to be all of the same size, which corresponds to the largest available cassette. A plurality of feed rollers are axially spaced on a drive shaft in the frame above each inserted cassette to feed sheets one by one from the cassette to an electrostatic copying machine or other printing machine.
The cassette is typically aligned against one side wall of the frame. Whereas the rollers are symmetrically positioned relative to the sheets in the cassette when the largest cassette is inserted in the frame, the rollers are asymmetrically positioned relative to the sheets when a narrower cassette is inserted in the frame. This results in skewed feeding of the sheets, jams and tearing.
Especially in an application in which several cassettes are inserted in the frame at once, it is necessary to provide some means for maintaining narrow cassettes rigidly in place and preventing all but the correctly sized cassette to be inserted in a particular space in the frame. These problems have remained heretofore unsolved in the prior art.